Choke control system for internal combustion engines

ABSTRACT

A system for controlling the choke valve of an internal combustion engine comprises a diaphragm box having therein a pair of diaphragms spaced apart from each other to define therebetween a liquid chamber which is filled with a liquid whose viscosity varies in accordance with temperature change. A partition wall having an orifice defined therethrough bisects the liquid chamber and negative pressure from the intake manifold of the engine acts upon one of the diaphragms to actuate the other of said diaphragms which has attached thereto an operating rod connected to the choke valve of the engine. The responsiveness of the control system varies with temperature as a result of the changing viscosity levels of the liquid contained within the liquid chamber.

[4 1 Sept. 23, 1975 CHOKE CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES[75] inventor: Masahiko Nakada, Toyota, Japan [73] Assignee: ToyotaJidosha Kogyo Kabushiki Kaisha, Japan [22] Filed: July 1, 1974 [21]Appl. No.: 484,872

[30] Foreign Application Priority Data July 6, 1973 Japan 48-75633 [56]References Cited UNITED STATES PATENTS 2,674,268 4/1954 Kimm 92/382,932,203 4/1960 Peters 3,190,623 6/1965 Ball 3,333,770 8/1967Freiberger 3,670,708 6/1972 Ojala 261/D1G. l8

3,739,760 6/1973 Charron 261/39 A 3,752,450 8/1973 Charron et al....261/39 R 3,791,358 2/1974 Masaki et al..... 123/119 F 3,800,762 4/1974McCullough 261/39 R Primary ExaminerTim R. Miles Attorney, Agent, orFirm-Toren, McGeady and Stanger [5 7] ABSTRACT A system for controllingthe choke valve of an internal combustion engine comprises a diaphragmbox having therein a pair of diaphragms spaced apart from each other todefine therebetween a liquid chamber which is filled with a liquid whoseviscosity varies in accordance with temperature change. A partition wallhaving an orifice defined therethrough bisects the liquid chamber andnegative pressure from the intake manifold of the engine acts upon oneof the diaphragms to actuate the other of said diaphragms which hasattached thereto an operating rod connected to the choke valve of theengine. The responsiveness of the control system varies with temperatureas a result of the changing viscosity levels of the liquid containedwithin the liquid chamber.

7 Claims, 3 Drawing Figures US Patent Sept. 23,1975

FIG. 3

FIG. 2

CHOKE CONTROL SYSTEM FOR'I NTERNAL COMBUSTION ENGINES BACKGROUND OF THEINVENTION The present invention relates generally to choke valve controlsystems for internal combustion engines and more particularly to asystem whereby the choke valve may be forcibly moved to its fully openedposition in response to negative pressure from the intake manifold ofthe engine.

Normally, during the phase of engine operation when an engine is not asyet sufficiently warmed up, fuel vaporization occurs at a lower rate andas a result combustion of the air-fuel mixture does not occur readily.It is therefore necessary under such operating conditions to supply aricher fuel mixture to the engine, and for this purpose there isordinarily utilized a choke valve which is adapted to throttle air flowat the inlet of the carburetor while drawing fuel in greater quantities.Such choke valve is usually fully opened when the engine has achieved asufficiently warm condition.

Automatic choke valves which are arranged to be gradually opened byautomatic action of a bimetallic member, which may be heated either byengine exhaust gas or by an electric heater, are commonly known. Morerecently, however, improvements have been developed in connection withthe engine warming mechanism which reduce the utility of the chokev'alvc. However, harmful components, such as CO and HC, occurring in theexhaust gases released from the engine will be present in greateramounts when the engine is not warmed up as compared to a condition whenthe engine is warmed up. Accordingly, it is desirable to quickly openthe choke valve at a point when the engine has achieved, to a certaindegree, its warm condition.

To this end, there has previously been proposed a choke valve openingdevice which utilizes a diaphragm mechanism operated by the vacuum fromthe intake manifold. Generally, when ambient temperature is low, alonger warming time is necessary than that required at normaltemperatures. Accordingly, under such low temperature conditions, thechoke valve must be opened slowly. However, in prior art choke valveopening systems, the choke valve will be always opened at the same speedand thus there occurs a likelihood that the operating condition of theengine at cold start will be impaired.

The present invention is directed toward overcoming such problems byproviding an improved choke valve control system which lowers the chokevalve opening speed in order to prolong the warming time of the engineat cold start and thereby enhance operating performance.

SUMMARY OF THE INVENTION Briefly, the present invention may be describedas a choke valve control system for an internal combustion engine whichincludes an intake manifold and a choke valve, said control systemcomprising, in combination, a diaphragm box, a pair of diaphragmslocated within said box and spaced apart from each other to define aliquid chamber therebctween, a liquid contained within said chamberadapted to undergo viscosity change in accordance with changes intemperature, a partition wall within said box bisecting said liquidchamber, orifice means defined through said partition wall, a chokevalve operating rod interconnected between one of said diaphragms andsaid choke valve and movable through an operating stroke betweenpositions into and out of driving engagement with said choke valve, adiaphragm chamber defined within said box by the other of saiddiaphragms on a side thereof opposite said liquid chamber, negativepressure conduit means connected between said intake manifold and saiddiaphragm chamber, and spring means biasing both said diaphragms towarda direction tending to place said operating rod out of drivingengagement with said choke valve. Introduction of the negative pressurein the diaphragm chamber is communicated through the liquid chamber todrive both the diaphragms in a direction tending to bring the operatingrod into driving engagement with the choke valve. When this occurs, thenegative pressure of the intake manifold is utilized to open the chokevalve. However, due to changes in' viscosity in the liquid containedwithin the liquid chamber, the responsiveness of the control system willbe alteredby'changing ambient temperature conditions, and accordingly alesser degree of choke valve opening willoccur during starting of anengine under low temperature conditions. The various features of noveltywhich characterize the invention are pointed out with particularity inthe claims annexed to and forming a part of this disclosure. For abetter understanding of the invention, its operating advantages andspecific objects attained by its use, reference should be had to theaccompanying drawings and descriptive matter in which there isillustrated and described a preferred embodiment of the invention.

DEscRIPTIoN OF THE DRAWING DETAILED DESCRlPTlON oF THE PREFERREDEMBODIMENT Referring now to the drawing there is shown in FIG. 1 acarburetor 1, an intake manifold pipe 2, an exhaust manifold 3 and athrottle valve 4 located within the body of the carburetor l. A chokevalve 5 is arranged to be controlled by a bimetallic member (not shown)which may be heated either by the exhaust gases of the engine or by anelectric heater. The choke valve 5 is mounted upon a choke valve shaft 6and a choke lever 7 having an elongated slot 8 is mounted upon the shaft6.

A choke valve control system 10 according to the present inventioncomprises a diaphragm box 1 l, a pair of diaphragms 12 and 13 which arespaced apart Within the box 1 1 to define therebetween a liquid chamber14, and a partition wall 15 located between the diaphragms 12 and 13bisecting the liquid chamber 14. The liquid chamber 14 maybe filled witha liquid which, for example, may be oil whose viscosity is varied inaccordance with variations in temperature. An orifice 16 is provided toextend through the partition wall 15 and a choke valve operating rod 17secured to one of the diaphragms 12 is interconnected between thediaphragm 12 and the choke valve 5. A vacuum conduit 19 connects theintake manifold 2 with a diaphragm chamber 18 defined within thediaphragm box 11 by the diaphragm 13 on a side of the diaphragm 13opposite the side of the liquid chamber 14.

Springs 20 and 21 are provided to normally bias both the diaphragms 12and 13 in a direction toward which the control system does not restrictmovement of the choke valve 5.

The choke valve operating rod 17 has one end loosely fitted in slidingengagement within the elongated slot 8 in the choke lever 7. Thus, withthe diaphragms 12 and 13 biased by the spring member 20 and 21 towardthe right, the right hand end of the operating rod 17 will be locatedwithin the slot 8 at a portion of its operating stroke through which therod 17 is out of driving engagement with the choke valve 5. When the rod17 is moved to the left, as viewed in FIG. 1, the right hand end thereofwill engage the end of the slot 8 thereby placing the rod 17 intodriving engagement with the choke valve 5.

A check valve 22 is provided on the partition wall and a valve 23 whichis arranged to be opened or closed in accordance with the operatingtemperature conditions of the engine is provided within the vacuumconduit 19.

In the operation of the choke valve control system in accordance withthe present invention, before the engine is started, the choke valvecontrol system will be in the condition depicted in FIG. 1. That is, thediaphragms 12 and 13 will be biased to the right as shown in FIG. .1 bythe springs and 21, respectively, and the choke valve operating rod 17will be out of driving engagement with the choke valve 5 by virtue ofits sliding engagement with the slot 8. Furthermore, the valve 23 in theconduit 19 will remain in its closed condition.

When the engine is started, the choke valve 5 will be controlled by thebimetallic member (not shown) regardless of the behavior of the chokevalve control system 10. However, when the engine has reached a specificlevel of warming, it is desirable to fully open the choke valve 5 inorder to reduce the harmful components in the exhaust gases. For thispurpose, the valve 23 is opened in response to the warmed-up conditionof the engine in order to communicate the intake manifold 2 with thediaphragm chamber 18. At this point, negative pressure in the diaphragmchamber 18 actuates the diaphragms 12 and 13 in order to drive the chokevalve 5 to its fully opened position against the force of the springs 20and 21 and against the flow resistance of an orifice 16 which is definedto extend through the partition wall 15.

Under such circumstances, if the temperature of the ambient air is at anormal level, the viscosity of the liquid within the liquid chamber 14will remain quite low so that the flow resistance of the orifice 16 isalso quite small. Accordingly, the diaphragms 12 and 13 will be quicklydrawn to the left, as viewed in FIG. 1, in order to fully open the chokevalve 5. This enables a quick decrease of harmful components in theexhaust gas.

On the other hand, if ambient air temperature is extremely low, theviscosity of the liquid in the liquid chamber 14 will be increased inaccordance with such ambient temperature and as a result the flowresistance of the orifice 16 will also be elevated. Thus, the diaphragms 12 and 13 will be drawn to the left more slowly in order therebyto effect a more gradual opening of the choke valve 5. This type ofoperation elongates the operating time of the choke valve and improvesthe characteristics of engine operation at cold start.

The check valve 22 located on the partition wall 15 is arranged suchthat it will be in the opened condition, as depicted in FIG. 2, when novacuum is applied in the diaphragm chamber 18, with the valve 22 beingactuated to its closed condition depicted in FlG. 3, when vacuum actsupon the diaphragm chamber 18. Thus, when vacuum in the diaphragmchamber 18 is released, the diaphragms 12 and 13 will be quicklyreturned to the positions thereof indicated in FIG. 1.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. A choke valve control system for an internal combustion engine whichincludes an intake manifold and a choke valve, said control systemcomprising, in combination, a diaphragm box, a pair of diaphragms lo-'cated within said box and spaced apart from each other to define withinsaid box a liquid chamber therebetween, said liquid chamber beingadapted to contain therein a liquid which will undergo viscosity changein accordance with changes in temperature, a partition wall within saidbox bisecting said liquid chamber, orifice means defined through saidpartition wall, a choke valve operating rod interconnected between oneof said diaphragms and said choke valve, and movable through anoperating stroke between positions into and out of driving engagementwith said choke valve, a diaphragm chamber defined within said box bythe other of said diaphragms on a side thereof opposite said liquidchamber, vacuum conduit means connected between said intake manifold andsaid diaphragm chamber, and spring means biasing both said diaphragmstoward a direction tending to place said operating rod out of drivingengagement with said choke valve whereby introduction of vacuum in saiddiaphragm chamber will be communicated through said liquid chamber todrive both said diaphragms in a direction tending to bring saidoperating rod into driving engagement with said choke valve.

2. A system according to claim 1 including a check valve located in saidpartition wall and adapted to open and close in response to vacuumapplied in said diaphragm chamber.

3. A system according to claim 1 including valve means located in saidconduit means and adapted to open and close in response to the operatingtemperature of said engine.

4. A system according to claim 2 wherein said orifice means comprise apair of orifices defined through said partition wall and wherein saidcheck valve comprises a member adapted to be moved to open and close oneof said orifices in response to vacuum applied in said diaphragmchamber.

5..A system according to claim 1 wherein said liquid contained withinsaid liquid chamber exhibits increasing viscosity levels with decreasingtemperature levels.

6. A system according to claim 1 wherein said operating rod is arrangedto move said choke valve toward its open position when brought intodriving engagement therewith.

7. A system according to claim 3 wherein said valve means is arranged toopen and to maintain said conduit means in flow communication betweensaid intake manifold and said diaphragm chamber when said engineoperating temperature is above a predetermined

1. A CHOKE VALVE CONTROL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE WHICHINCLUDES AN INTAKE MANIFOLD AND A CHOKE VALVE. SAID CONTROL SYSTEMCOMPRISING, IN COMBINATION, A DIAPHRAGM BOX, A PAIR OF DIAPHRAGMSLOCATED WITHIN SAID BOX AND SPACED APART FROM EACH OTHER TO DEFINEWITHIN SAID BOX A LIQUID CHAMBER THEREBETWEEN, SAID LIQUID CHAMBER BEINGADAPTED TO CONTAIN THEREIN A LIQUID WHICH WILL UNDERGO VISCOSITY CHANGEIN ACCORDANCE WITH CHANGES IN TEMPERATURE, A PARTITION WALL WITHIN SAIDBOX BISECTING SAID LIQUID CHAMBER, ORIFICE MEANS DEFINED THROUGH SAIDPARTITION WALL, A CHOKE VALVE OPERATING ROD INTERCONNECTED BETWEEN ONEOF SAID DIAPHRAGMS AND SAID CHOKE VALVE, AND MOVABLE THROUGH ANOPERATING STROKE, BETWEEN POSITIONS INTO AND OUT OF DRIVING ENGAGEMENTWITH SAID CHOKE VALVE, A DIAPHRAGM CHAMBER DEFINED WITHIN SAID BOX BYTHE OTHER OF SAID DIAPHRAGMS ON A SIDE THEREOF OPPOSITE SAID LIQUIDCHAMBER, VACUUM CONDUIT MEANS CONNECTED BETWEEN SAID INTAKE MANIFOLD ANDSAID DIAPHRAGM CHAMBER, AND SPRING MEANS BIASING BOTH SAID DIAPHRAGMSTOWARD A DIRECTION TENDING TO PLACE SAID OPERATING ROD OUT OF DRIVINGENGEGEMENT WITH SAID CHOKE VALVE WHEREBY INTRODUCTION OF VACCUM IN SAIDDIAPHRAGM CHAMBER WILL BE COMMUNICATED THROUGH SAID LIQUID CHAMBER TODRIVE BOTH SAID DIAPHRAGMS IN A DIRECTION TENDING TO BRING SAIDOPERATING ROD INTO DRIVING ENGAGEMENT WITH SAID CHOKE VALVE.
 2. A systemaccording to claim 1 including a check valve located in said partitionwall and adapted to open and close in response to vacuum applied in saiddiaphragm chamber.
 3. A system according to claim 1 including valvemeans located in said conduit means and adapted to open and close inresponse to the operating temperature of said engine.
 4. A systemaccording to claim 2 wherein said orifice means comprise a pair oforifices defined through said partition wall and wherein said checkvalve comprises a member adapted to be moved to open and close one ofsaid orifices in response to vacuum applied in said diaphragm chamber.5. A system according to claim 1 wherein said liquid contained withinsaid liquid chamber exhibits increasing viscosity levels with decreasingtemperature levels.
 6. A system according to claim 1 wherein saidoperating rod is arranged to move said choke valve toward its openposition when brought into driving engagement therewith.
 7. A systemaccording to claim 3 wherein said valve means is arranged to open and tomaintain said conduit means in flow communication between said intakemanifold and said diaphragm chamber when said engine operatingtemperature is above a predetermined level.